The present invention relates to a thin film magnetic head, and, in particular, to its manufacturing method which is suitable for high precision gap depth machining.
When a conventional thin film magnetic head is subjected to gap depth machining, the machining distances are defined on the basis of a sensing pattern for a gap depth machine operation (hereafter, referred to as the sensing pattern) instead of the actual device. Accordingly, deviations between the actual device and the sensing pattern are incurred. Depending upon precision in alignment of devices, for example, gap depth dimensions are disadvantageously deviated from the typical value. A large gap depth dimension results in an insufficient recording magnetic field for the recording medium. Effecting gap depth machining further beyond the zero position where the gap depth is zero increases the gap length and exposes an organic resin to the medium side face, resulting in a poor crash resistance, i.e., a poor resistance to crash due to collision between the head and a disk.
A method for improving the crash resistance was proposed in unexamined Japanese Patent Publication No. 98822/83. This method, though relating to a thin film head of the type having a double layer coil, will now be described by referring to FIG. 1. FIG. 1 is a sectional view of a thin film magnetic head having two coil layers. After a base film 12 made of alumina or the like has been formed on a substrate 11, a lower magnetic substance 13, an insulative layer 20, a first coil layer 15, an insulative interlayer film 16 of an organic resin, a gap material 14 of an inorganic material such as alumina, a second coil layer 15, an insulative interlayer film 19 of an organic resin, and an upper magnetic substance 17 are successively laminated. Since the front end of the insulative interlayer film 16 between the gap material 14 and the insulative layer 20 stands back from the zero position of magnetic gap depth (position A'), the organic resin is not exposed to the air bearing surface, i.e., to the medium side face even if the laminate is subjected to machining from the medium side face to the position A' in a direction C', resulting in an improved crash resistance. Further, in FIG. 1, the insulative interlayer film 16 between the gap material 14 and the insulative layer 20 is not caused to stand back so much as the film 19, partly because the film 16 is covered by the gap material 14 and partly because even if it were caused to stand back, nothing would be provided for facilitating detection of the machining distance thereby. In a method disclosed in unexamined Japanese Patent Publication No. 111116/83, an insulative interlayer film between upper and lower magnetic substances is so formed by laminating an inorganic insulative material and an organic insulative material that only the inorganic insulative material is exposed to the medium side face when the laminate is subjected to machining as far as a position where the magnetic gap depth becomes zero. As a result, the crash resistance is improved.
However, it is still difficult to stably produce a thin film magnetic head which is small in gap depth dimension, high in the gap depth accuracy, and excellent in crash resistance.